Will bubbles burst the algal blooms in Hawke's Bay's Lake Tutira?

The air curtain trial began in September 2017 with the installation of a perforated pipe - like an aquarium oxygen bubbler - into Lake Waikopiro. Photo / Supplied.

A trial that has turned a Hawke's Bay lake to a bubble-filled aquarium of sorts, in a bid to prevent algal blooms, has had mixed results.

Hawke's Bay Regional Council has been trialling an air curtain in Lake Waikopiro at Tūtira, but scientists say the results are so far inconclusive on whether its a solution to fix the lake's long-term water quality.

Lake Tūtira sits in a dynamic natural environment, heated aggressively by the sun in summer, situated in a natural bowl with small flows in and out of the lake.

Due to little natural mixing of the water and a high loading of nutrients often leads to algae blooms. Yet, both lakes have long been popular for recreation and fishing with Tūtira Regional Park a well-known and popular camping destination.

The 50 metre long air curtain was installed into Lake Tūtira's smaller neighbour - Lake Waikopiro - in 2017 and has been constantly monitored by regional council scientists as they test for the effectiveness and the best ways to operate it.

The curtain is part of a long term project called Te Waiū o Tūtira - the milk of Tūtira - which refers to an abundance of kai and spiritual sustenance derived from Lake Tūtira.

The curtain trial involves a partnership with the Maungaharuru-Tangitu Trust, landowners and the local community, all of which work with the regional council.

After two bubbling seasons, initial analysis showed that the air curtain mixed the lake water, which was its purpose. But the project's governance group is still deciding whether to invest up to $200,000 to deploy a new and bigger air curtain into Lake Tūtira.

At its widest point, the lake spreads to 1.2km, but the streams that sustain its life force flow too closely to each other and over-time, sediment in-flows have clogged the lake with the nutrient levels remaining high.

The project leaders aim to fix the basic yet complex elements, including the land use where run-off has a direct effect on the lake's health and function.

Te Waiū o Tūtira's work plan includes growing the possibility of creating a new southern outlet to improve water mixing and access for eels, a logging and planting plan that protects the lake from potential forest sediment, working with landowners to plant trees and improve farm plans as well as thinking of ways to reconnect Papakiri Stream (Sandy Creek) to the lake at low flows.

For now, the project will continue to simmer away, with regional council scientists monitoring its progress.